Method of constructing marine float structures

ABSTRACT

A method of constructing a marine float structure, such as a large-sized ship structure, is accompolished by assembling a number of divided ship portions on a ship building base. The first divided portion is transported on the water surface by means of a composite pontoon which is so constructed that each individual portion thereof can be separated from the other up and down or forwardly and backwardly. Then the composite pontoon is caused to sink down in the water so that said first divided portion of the ship can float of its own accord on the water surface. Subsequently the second divided portion of the ship is transported on the water surface using the same pontoon as mentioned above. A part of the composite pontoon is separated from the remaining body and allowed to sink down in the water while said second divided portion of the ship is held by the remaining portion of the pontoon. The separated part of the pontoon is used to float said first divided portion of the ship on the water surface, thereby combining both divided portions of the ship in a single unit on the water surface.

United States Patent Takezawa et al.

[ 51 July 11, 1972 [54] METHOD OF CONSTRUCTING MARINE FLOAT STRUCTURES[72] inventors: lsoe Takmwa; Mmtaro Mute; Koichl I-lorl, all ofNagasaki, Japan [21 1 Appl. No; 40,520

[30] Foreign Application Priority Data June 5, 1969 Japan ..44/44l98[52] [1.8. CI. ..l14/65 R [51 Int. Cl t i l l l l ..B63b 9/00 [58] FieldolSearch 14/65 R, 65 A,77 R, 77 A,

114/44-46. 49, 0.5 F, 0.5 R, 66.5 F; 61/64-68; 9/8

FOREIGN PATENTS OR APPLICATIONS 1,953,753 6/1970Germany.......l......................l14/77R 97,144 ll/l960 Norway..ll4/6$R Primary Examiner-Duane A. Reger Assistant ExaminerF. K. YeeAttorney-Otto John Munz 1 1 ABSTRACT A method of constructing a marinefloat structure, such as a large-sized ship structure, is accompolishedby assembling a number of divided ship portions on a ship building baseThe first divided portion is transported on the water surface by meansof a composite pontoon which is so constructed that each individualportion thereof can be separated from the other up and down or forwardlyand backwardly. Then the composite pontoon is caused to sink down in thewater so that said first divided portion of the ship can float of itsown accord on the water surface. Subsequently the second divided portionof the ship is transported on the water surface using the same pontoonas mentioned above. A part of the composite pontoon is separated fromthe remaining body and allowed to sink down in the water while saidsecond divided portion of the ship is held by the remaining portion ofthe pontoon The separated part of the pontoon is used to float saidfirst divided portion of the ship on the water surface, therebycombining both divided portions of the ship in a single unit on thewater surface.

2 China, 10 Drawing Figures PKTENTEDJUL n 1972 3,675,606

sum 1 or 3 4/\ SM TA TF Fg [NV/LIN 1 HR 51 ISOE TAKEZAWA, MASATARO MUTO,KOICHI HORI PATENTEnJuL 11 m2 3. 675.606

saw 2 or 3 FIG. 4

INVENI 0R 5 ISOE TAKEZAWA, MASATARO MU'IO, KOICHI HORI P'A'TENTEDJUL 1 1I972 SHEET 3 OF 3 l NVEN'I UP S ISOE TAKEZAWA, MASATARO MUTO, KOICHIHORI BACKGROUND OF THE INVENTION The present invention relates to amethod of ship building and more particularly to a method ofconstructing a largesized ship structures such as a marine vessel byutilizing economical equipment that does not use an inclined shipbuilding base or dock.

In recent years, there is a trend of building marine vessels ships inlarge sizes. Since there are a number of technical problems with usingan inclined ship building base to construct large-sized marine vessels,a ship constructing dock is generally used instead of a ship buildingbase. However. enormous expense and considerable time are requiring inerecting a ship constructing dock. In some instances it is substantiallyimpossible to construct such a large-scale dock by virtue of thegeographic conditions of a shipyard.

In view of the above conditions, it has heretofore been proposed as analternative procedure in ship building to carry out the launching of aship by the use of an inclined carriage or using pontoons. In the caseof the inclined procedure, a sliding surface or rolling surface isrequired to slide the hull down onto the water surface. Further, thecost of this type of equipment is high. Further, the inclined carriageis liable to twist during the descent of the hull.

According to a conventional method for constructing a hull on ahorizontal ship building base using a quay and launching it by means ofa pontoon, it is unavoidable that such pontoon must be of a in greatlength. Namely, accordingly to this method, as shown in FIG; 1, theheight h of the surface of the ship building base 01 mounted on adry-land type foundation from the water surface (L.W.L.) at low tideshould be at least 4 meters by adding an allowance of the water line(draft) about I m to the difference 3 In between the periods of low andhigh tides.

On the other hand, a hull S constructed on the ship building base 01 canbe transferred onto the pontoon only by maintaining the upper surface ofthe pontoon P and the surface of the ship building base 01 at equalheights. Consequently it becomes necessary to have the pontoon P withthe hull mounted thereon exposed at least 4m above the water surface.For this purpose, the entire height H of the pontoon with the additionof deepness below the draft line should be at least twice as much as theabove-mentioned it, that is, at least about 8 m. Needless to say thebasis of this calculation has been referred to in the case of using apontoon corresponding to the entire length ofthe hull S.

As a result, the conventional methods require the pontoon P itself to besufficiently large-sized so that the manufacturing cost becomes veryhigh. Also, a large-sized hull S that is constructed all on a horizontalship building base is rather difficult to be transferred onto thepontoon P, and is thus an extremely complicated and time consumingoperation.

SUMMARY OF THE INVENTION The object of the present invention is toprovide a method of manufacturing a large-sized building base withoutthe above-mentioned disadvantages.

A further object of the present invention is to provide a method ofconstructing marine float structures, comprising the construction oflarge-sized marine float structures such as large-sized tankers in asuitable number of separately divided portions on a horizontal shipbuilding base by utilizing the facilities of a quay and the use ofcomposite pontoons formed of many up-and down or forwardly and/orbackwardly separable portions wherein; flrst of all, the first dividedportion of the hull is transported onto the water surface; then thecomposite pontoon is caused to sink down in the water to launch saidfirst divided portion; subsequently, the second divided portion istransported onto the water surface using the same composite pontoon butin this case a portion of the composite pontoon is separated therefromso as to sink down in the water and said second divided portion is heldin condition exposed above the water surface by means of the remainingportions of the composite pontoon; and simultaneously said first dividedportion is caused to float exposed above the water using said separatedportion of the pontoon so that both divided portions can be jointed onthe water surface.

Other objects and advantages of the present invention will becomeapparent from the following description with reference to embodiments inthe construction of a large-sized tanker.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view showing anexample of a launching procedure using a pontoon of the conventionaltype.

FIGS. 2 through 7 are views showing a construction of a marine floatstructure according to a first embodiment of the present invention, FIG.2 is a perspective view of a composite pontoon.

FIG. 3 is a side view of a hull which is constructed in divided form.

FIGS. 4 through 7 are side views showing examples of a constructionsteps.

FIGS. 8 through 10 show a second embodiment of the present invention.

FIG. 8 is a perspective view of another composite pontoon.

FIG. 9, and 10 are side views showing examples of construction steps.

DETAILED DESCRIPTION OF THE INVENTION With reference to FIGS. 2 through7 showing a first embodiment of the present invention, B indicates analmost horizontal ship building base constructed by utilizing a quay,and the hull S is to be constructed thereon in the form of a number ofdivided portions in the direction of fore and aft parts of the ship.

The height of the ship building base B is determined in such a mannerthat the upper surface of the base 8 cannot be immersed in the water athigh tide or by the high waves.

As an example, assume the difference in tidal position to be 3 m at lowand high tides and adding the allowance draft line thereto, the height hof the ship building base B from the water surface at low tide will becomputed to be about 4 m.

The character P indicates the composite pontoon for use in thisembodiment and said pontoon P consists of two unit pontoons P and Pwhich are overlapped in the manner of being separated from each other.These unit pontoons P and I are partitioned inside in the form of aplurality of areas to constitute a number of float chambers l and 2.

These float chambers l and 2 are adapted to communicate with respectivepipes for pouring and discharging water (not shown in the drawing). sothat it is possible to adjust the buoyancy and trimming of each pontoonby pouring water into, or discharging it from, each float chamber. It isto be noted that the above-mentioned water pouring and dischargingapparatus is of conventional construction. The size of the compositepontoon P is such that its length L is about one half of the length of avessel to be constructed. Its depth H is about two times the abovementioned height h namely, about 8 m, in order that the upper surface ofthe composite pontoon may be held in level with the surface of the shipbuilding base B even when tidal position is the lowest and the head dropbetween the water surface and the surface of the ship building base Bamounts to a maximum (about 4 m).

When a tanker is constructed using the above-mentioned composite pontoonP and the horizontal ship building base, the hull S is constructed onthe ship base building B base in the form of four divided parts such asthe fore part F, fore half part tank TF, aft half part tank TA and aftpart A, as shown in FIG. 3.

Subsequently, the composite pontoon P is brought forwardly of the shipbuilding base B and then ballast water is poured into, and dischargedfrom, each float chamber I and 2 in a suitable manner so that the uppersurface of the composite pontoon P is adjusted to assume the same heightas the surface of the ship building berth.

After this operation has been accomplished, the fore part F and the forehalf part tank TF are transferred onto the abovementioned pontoon P.

For this purpose, a transfer carriage is used though it is notillustrated in the drawing.

ALong with the progress of this transfer mounting, gravitation acting onthe composite pontoon is gradually increased so that it is necessary todischarge the ballast water from each float chamber 2, in order tomaintain the draft and trimming of the composite pontoon P. In certaininstances, as shown by the imaginary line, there is provided a base seat3 at the bottom of the water beforehand and then the composite pontoon Pis brought into contact with the base seat 3 to make use of astabilizing operation effectively.

In this way, when the fore part F and the fore half part tank TF havebeen mounted on the composite pontoon by transfer, they are jointed bywelding or the like thereon to complete the fore part SF of the hull.The fore part F and the fore half part tank TF are jointed after theyhave been mounted on the composite pontoon to facilitate their mountingon the composite pontoon P. If necessary, both may be jointed on theship building base B beforehand and it is also possible to constructthem in a body from the beginning without preparing them in dividedform.

As mentioned above, in the event that the fore part F and the fore halfpart tank TF are mounted on the composite pontoon by transfer and arejointed together to complete the fore ship portion SF, the combined unitis transported onto the water surface by means of a towboat or the likewhile mounting it on the pontoon. Then ballast water is poured into eachfloat chamber 1 and 2 of the pontoon in a suitable position so that itcan sink down and the fore ship portion SF only can float of its ownaccord on the water surface.

Subsequently, as shown in FIG. 5, the aft half part tank TA and the aptpart A are mounted on the pontoon by transfer in exactly the same mannerusing the same pontoon as mentioned above and they are jointed togetherto complete the aft ship portion SA, which is then transported onto thewater surface by means of a towboat or the like.

Thereafter, as shown in FIG. 6, ballast is suitably poured into eachfloat chamber 2 of the lower half unit pontoon P constituting thecomposite pon pontoon that only the unit pontoon P is caused to sinkdown in the water and be separated from the other unit pontoon P,

As a result, the fore ship portion SA is destined to be supported by thebuoyancy of the unit pontoon l Then only but the whole body is allowedto remain as exposed above the water surface except that the height fromthe water surface is reduced.

Consequently, the separated unit pontoon 2 is brought right below thefore ship portion SF by means of a towboat or the like. Then the ballastwater in each float chamber 2 is suitably discharged therefrom until thefore ship portion SF is allowed to float and be exposed above the watersurface.

Then, as shown in FIG. 7, both ship portions are drawn together andtheir corresponding joint portions are caused to engage each other sothat both portions are jointed on the water surface to complete the hullS.

As mentioned above, it is necessary that a pontoon of great depth beused to compensate for the head drop h between the water surface and thesurface of the ship building base when the fore ship portion SF and theaft ship portion SA are mounted on the pontoon by transfer asexemplified in this embodiment. But, once both ship portions SF and SAare transported onto the water surface for the purpose of jointing themon the water surface, it is no longer necessary to use the abovementioned pontoon of great depth. So, attention is drawn to the factthat it is possible to achieve the same purpose sufficiently by usingthe pontoon of about half of the above mentioned depth. For thispurpose, to begin with, when the fore ship portion SF and the aft shipportion are transferred from the ship building base onto the watersurface, the unit pontoons P, and P, are overlapped to increase thedepth of this assembly to achieve the required purpose. Thereafter bothpontoons are separated from each other so that the fore ship portion SFand the aft ship portion SA can float and be exposed above the watersurface for achieving their joint effect.

Now, a second embodiment of the present invention will be explained indetail with reference to FIGS. 8 through 10.

In this embodiment, as an example, the composite pontoon P consists offine unit pontoons P,-P, which can be divided forwardly and backwardlyas shown in FIG. 8.

The size of this composite pontoon is illustrated to show that itslength 1. is about one half of the ships length. Its depth H shows thatit is about twice the height it between the surface of the ship buildingbase and the water surface at low tide.. This is accomplished in thesame manner as the aforesaid em bodiment, which has already beendescribed in detail.

Though not shown in the drawing, there are provided a plurality ofpartitioned float chambers in all the respective unit pontoons P,-P, inthe saMe manner as the afore-explained embodiment. Therefore, it ispossible also to adjust buoyancy and trimming by suitably pouring waterinto, or discharging it from, each float chamber. Also it is possible toprovide means for communicating a float chamber with another.

In order that a ship be constructed using the above mentioned pontoon P,as described in the afore-said embodiment, the hull is constructed individed form on the ship building base, Then as shown in FIG. 9, thefore ship portion SF is transferred onto the water surface. The ballastwater is uniformly poured into the float chamber of each unit pontoonP,P,, to cause the pontoon P to sink down in order to permit thefloating of the fore ship portion SF of its own accord on the watersurface. Then, the same composite pontoon is used again to transport theaft ship portion SA onto the water surface. Under these conditions, asshown in FIG. 10, ballast water is poured into the float chamber of eachunit pontoon P P and P, respectively and these unit pontoons areseparated from the other unit ones P, and P, so that the fore shipportion SA is supported by the latter two unit pontoons P and P only.

Subsequently, the separated unit pontoons P,, P;, and P are suitablypositioned right beneath the fore ship portion SF after which theballast water in the float chambers of the unit pontoons P,, P; and P,are discharged therefrom to float and expose the fore ship portion SF onthe water surface.

Under these conditions, both portions SF and SA are drawn close to eachother and jointed by welding to complete the hull S.

[n the embodiment, five unit pontoons are used in such a manner thatthere unit pontoons are arranged for the fore ship portion and two unitpontoons for the afi ship portion because of which there occurs animbalance of buoyancy of both ship portions in certain instances.Therefore, in such cases, as shown in FIG. 10, it is also renderedpossible to carry out the jointing operation with the hull S beingsomewhat inclined.

As has been described hereinbefore, with reference to the two concreteembodiments of the present invention, the application of this method isnot limited to the construction of ships or marine vessels but it can beextensively applied to the construction of marine float structures, forexample, such as transport barges, floating docks and other marinestructures.

In brief, the present invention is intended to provide a method ofmanufacturing marine float structures, comprising constructinglarge-sized marine float structures in suitably divided form on ahorizontal ship building base and using composite pontoons consisting ofmany up-and'down or forwardly and/or backwardly separable portions,wherein firstly, the first divided portion of the structure istransported onto the water surface, then said composite pontoon iscaused to sink down in the water to permit the floating of said firstdivided portion of the structure of its own accord on the water surface,successively, the second divided portion of the structure is alsotransported onto the water surface using the same pontoon, a part ofsaid pontoon is separated from the whole body and causing to sink downin the water, said second divided portion of the structure is held onthe water surface using the remaining part of the pontoon and the sametime, the firstly separated part of 5 the pontoon is used to float saidfirst divided portion of the structure on the water surface and tosupport it thereon and finally, both divided portions of the structureare drawn close to each other so that they can be jointed together onthe water.

According to the present invention, the following advantages will beanticipated.

a, It is possible to construct large-sized float structures such asmarine vessels without using an inclined ship building base or shipbuilding dock so that various technical and economical problems involvedin the use of an inclined ship building berth or dock can be extensivelysolved in a satisfactory manner.

b. As compared with the conventional methods of ship launching, whichhave heretofore been proposed using pontoons, the present inventionmakes it easily possible to construct structures of almost the samesizes as conventional structures using pontoons of about half sized ofalso conventional pontoons, thereby proving the method of the presentinvention to be considerably reasonable and economical.

c. After the structure has been constructed in suitably sized anddivided form on an almost horizontal ship building base, each portion isseparately transferred onto the pontoon for mounting thereon. Thus, theoperation of trans ferring portions of the structures onto the pontoonis rendered very easy.

We claim:

1. A method of ship building for constructing large-sized shipstructures, comprising the following steps:

the first step includes providing at least a first ship portion and asecond ship portion for constructing a ship on a ship building base,said ship building base being mounted on a dry-land type foundation;

the second step includes constructing the ship portions and transportingsaid first constructed ship portion onto a water surface using acomposite pontoon as a support thereof, thereafter said compositepontoon being suck so as to float said first portion on the watersurface by its own buoyancy without the aid of the composite pontoon,said composite pontoon being constructed in a horizontal stack with aplurality of individually detachable unit pontoons,

the height of said composite pontoon being made sufficient to compensatefor the intervening height difierence between the level of the watersurface and the level of the ship building base whenever either one ofthe ship portions is drawn from said base onto the water surface, andeach of said unit pontoons layered into the composite pontoon having asufficient buoyancy of its own to hold each of said ship portions withpositive buoyancy supported from beneath;

the third step includes transporting said second constructed shipportion onto the water surface using said composite pontoon as a supportthereof, separating the composite pontoon into its upper and lower unitpontoons, supporting said second ship portion with the upper unitpontoon and removing the lower unit pontoon therefrom;

the fourth step includes said first buoyant constructed shi portionbeing supported in a floating state on the water surface with the aid ofsaid first sunken one of the unit pontoons after regaining its ownpositive buoyancy; and

the fifth step includes both first and second floated ship portions withthe aid of both first and second unit pontoons respectively being drawnto each other and welded together so as to unify them into a single shipunit while being held on the water surface.

2. A method of ship building according to claim 1, wherein saidcomposite pontoon consists of a plurality of up-and-down separableportions.

III I I

1. A method of ship building for constructing large-sized shipstructures, comprising the following steps: the first step includesproviding at least a first ship portion and a second ship portion forconstructing a ship on a ship building base, said ship building basebeing mounted on a dryland type foundation; the second step includesconstructing the ship portions and transporting said first constructedship portion onto a water surface using a composite pontoon as a supportthereof, thereafter said composite pontoon being suck so as to floatsaid first portion on the water surface by its own buoyancy without theaid of the composite pontoon, said composite pontoon being constructedin a horizontal stack with a plurality of individually detachable unitpontoons, the height of said composite pontoon being made sufficient tocompensate for the intervening height difference between the level ofthe water surface and the level of the ship building base whenevereither one of the ship portions is drawn from said base onto the watersurface, and each of said unit pontoons layered into the compositepontoon having a sufficient buoyancy of its own to hold each of saidship portions with positive buoyancy supported from beneath; the thirdstep includes transporting said second constructed ship portion onto thewater surface using said composite pontoon as a support thereof,separating the composite pontoon into its upper and lower unit pontoons,supporting said second ship portion with the upper unit pontoon andremoving the lower unit pontoon therefrom; the fourth step includes saidfirst buoyant constructed ship portion being supported in a floatingstate on the water surface with the aid of said first sunken one of theunit pontoons after regaining its own positive buoyancy; and the fifthstep includes both first and second floated ship portions with the aidof both first and second unit pontoons respectively being drawn to eachother and welded together so as to unify them into a single ship unitwhile being held on the water surface.
 2. A method of ship buildingaccording to claim 1, wherein said composite pontoon consists of aplurality of up-and-down separable portions.